This invention relates to a barge-carrying waterborne vessel and to a barge-transporting system, as well as to a method for transporting barges across the seas.
In our U.S. Pat. No. 3,913,512, issued Oct. 21, 1975, we describe a vessel which had its primary use in relatively shallow or coastal waters. It employed flotation loading and unloading of barges and utilized transfer of buoyancy from the barges to the vessel in a hold normally kept flooded to the vessel's waterline. The present invention is directed to a flotation-loaded-and-unloaded vessel useful where a substantial width of ocean is to be crossed. In most such instances, it is preferred to pump out the holds so that they are substantially dry, although, if desired, the invention may be used with the hold kept in constant communication with the sea.
It is important for the barges (the term "barges" as used herein is used broadly and includes buoyant cargo carriers which may not strictly be barges in the narrow sense of the word but which are floatable and buoyant cargo carriers capable of flotation loading and unloading) to be retained so that there will be no relative movement between them and the vessel during transport. This enables the phenomenon of transfer of buoyancy, noted in our earlier patent, to be taken advantage of in the event that the hold becomes flooded accidentally, as well as in instances where the hold is flooded throughout the voyage. Such transfer of buoyancy provides the vessel with the ability to sustain damage resulting in accidental flooding of each barge hold, the buoyancy of the barges being transferred to the carrying vessel via a barge-retention or hold-down system. This feature qualifies the carrying vessel for higher seaworthy standards, as designated by marine classification societies. In this connection, the present invention seeks to provide improved method and apparatus for retaining the barges in place in a manner involving a lower initial expense and reduced expense of operation and maintenance.
One of the difficulties encountering any system in which barges are to be transported, is the expense of loading and unloading. As already indicated, the present invention, like that of the issued U.S. Pat. No. 3,913,512, provides flotation loading and unloading through a gate in the vessel. However, the present invention also provides for movement of the barges within the vessel to be accomplished by utilizing the flow of seawater in the hold. The flow is away from the gate during the loading and toward it during unloading. This novel system enables the lowering of both capital expense and the expense of operation and maintenance.
For some types of operation it is desirable to have a plurality of barge-receiving holds. To some extent, this has already been shown in our U.S. Pat. No. 3,978,806, which issued Sept. 7, 1976, but here again the present invention provides an improved type of plural-hold construction. Two kinds of systems are provided, one in which the holds are completely separate and have separate gates (as in U.S. Pat. No. 3,978,806), which enables the vessel to carry barges or pontoons of any length, up to and including the full length of the barge hold and thereby to render a type of service which cannot be rendered by other types of barge-carrying vessels. In the other system there is only one gate, having approximately the width of one of the holds; this latter system includes a transfer arrangement by which the barges are moved laterally into one or another of the holds. This is combined, of course, with the novel system of using water flow for fore-and-aft movement.
Thus, among the objects of the present invention are these: to provide an improved system employing flotation loading and unloading in which water flow is used for moving the barges inside the vessel; to provide a novel type of plural hold system; to provide a novel retention means or hold-down system; and to provide an improved and less expensive over-all barge transportation system and a novel method of operation.
The invention also seeks to provide an improved type of barge which can be mated with the barge-carrying vessel to enable an extraordinarily simple and effective means of retaining the barges in place in the vessel's hold.